It is known in the art to produce an airflow using electro-kinetic techniques, by which electrical power is converted into a flow of air without mechanically moving components. One such system was described in U.S. Pat. No. 4,789,801 to Lee (1988), depicted herein in simplified form as FIG. 1. System 100 includes a first array 110 of emitter electrodes 112 that are spaced-apart symmetrically from a second array 120 of collector electrodes 122. The positive terminal of a high voltage pulse generator 140 that outputs a train of high voltage pulses (e.g., 0 to perhaps +5 KV) is coupled to the first array 110, and the negative pulse generator terminal is coupled to the second array 120 in this example.
The high voltage pulses ionize the air between arrays 110 and 120, and create an airflow 150 from the first array 110 toward the second array 120, without requiring any moving parts. Particulate matter 160 in the air is entrained within the airflow 150 and also moves towards the collector electrodes 122. Some of the particulate matter is electrostatically attracted to the surfaces of the collector electrodes 122, where it remains, thus conditioning the flow of air exiting system 100. Further, the corona discharge produced between the electrode arrays can release ozone into the ambient environment, which can eliminate odors that are entrained in the airflow, but is generally undesirable in excess quantities.
In a further embodiment of Lee shown herein as FIG. 2, a third array 230 includes passive collector electrodes 232 that are positioned midway between each pair of collector electrodes 122. According to Lee, these passive collector electrodes 232, which were described as being grounded, increase precipitation efficiency. However, because the grounded passive collector electrodes 232 (also referred to hereafter as driver electrodes) are located close to adjacent negatively charged collector electrodes 122, undesirable arcing (also known as breakdown or sparking) will occur between collector electrodes 122 and driver electrodes 232 if the potential difference therebetween is too high, or if a carbon path is produced between an electrode 122 and an electrode 232 (e.g., due to a moth or other insect that got stuck between an electrode 122 and electrode 232). It is also noted that driver electrodes are sometimes referred to as interstitial electrodes because they are situated between other (i.e., collector) electrodes.
Increasing the voltage difference between the emitter electrodes 112 and the collector electrodes 122 is one way to further increase particle collecting efficiency and air flow rate. However, the extent that the voltage difference can be increased is limited because arcing will eventually occur between the collector electrodes 122 and the driver electrodes 232. Such arcing will typically decrease the collecting efficiency of the system, as well as produce an unpleasant odor.
Accordingly, there is a desire to improve upon existing electro-kinetic techniques. More specifically there is a desire to increase particle collecting efficiency and airflow rate, and to reduce arcing between electrodes.